Generally, in a feedstock fluid supply device in a semiconductor manufacturing device or the like, it is required to supply a process feedstock fluid with a stable concentration into processing equipment to improve the quality of semiconductor products.
Accordingly, in conventional feedstock fluid supply devices of this type, for example, a bubbling type feedstock fluid supply device as shown in FIG. 9, a photometric analysis type concentration meter 22 is provided in the vicinity of a feedstock vapor outlet of a feedstock tank 21 at a controlled temperature, and the temperature in the feedstock tank 21, the flow rate of a carrier gas CG, the vapor pressure Po in the tank and other conditions are adjusted by a concentration detection signal from the concentration meter 22, whereby a process gas 24 at a predetermined feedstock concentration (for example, process gas containing an organic metallic material vapor such as trimethylgallium TMGa accumulated in the tank 21) is supplied into a reaction furnace 23.
It should be noted that in FIG. 9, reference numeral 25 denotes a thermal massflow controller, and reference numeral 26 denotes a pressure adjustment device for the pressure in the tank.
As the concentration meter 22 of the above-mentioned photometric analysis system, the concentration meter 22 with various configurations have been put into practical use, but most of the concentration meter 22 is formed by, as shown in FIG. 10 (Japanese Unexamined Patent Publication No. H9-178652) and FIG. 11 (Japanese Unexamined Patent Publication No. 2004-108981), an optical cell (gas cell) 27, through which a gas G to be measured flows, a light source 28 radiating a light beam into the optical cell 27, a photoreceiver 29 of the light beam passed through the inside of the optical cell 27, an arithmetic unit 30 which determines the absorbance from a signal of the photoreceiver 29 to calculate the concentration of the feedstock, and other components. It should be noted that reference numeral 31 denotes a main pipeline, and reference numeral 32 denotes a branch pipeline.
Such a concentration meter is configured to measure the so-called absorbance of the gas in the optical cell 27 and to calculate the gas concentration by applying the Lambert-Beer law to the measurement results of the absorbance.
In addition, in the latter Japanese Unexamined Patent Publication No. 2004-108981, as shown in FIG. 11, it is so configured that an in-line sensor 33 having an optical cell (absorbance cell) integrated therein is fixed to a pipeline 31, and the photometric measurement of the light passed through the above-mentioned optical cell is performed.
It should be noted that the concentration meter 22 of the above photometric analysis system itself is already known, and their detailed explanation will be omitted herein.
Then, in measuring the concentration of the feedstock gas, first, it is necessary to connect and fasten the optical cell 27 to the pipeline 32 (or pipeline 31), but ensuring airtightness of the connection portion between the optical cell 27 and the pipeline 32 (or pipeline 31) is not easy. For example, it is difficult to fasten the connection with high airtightness in usual screw connection and flange connection by using packing materials or seal materials, and the problem is that it is not easy to obtain the air tightness (external leakage 1×10−10 Pa·m3/sec or lower) required in the field of semiconductor manufacturing devices.
Moreover, in order to continuously perform stable gas concentration measurement for a long period of time, various structures forming the optical cell 27, for example, a light transmission window material, need to be firmly fastened and retained onto the main body of the optical cell 27 with high airtightness. Therefore, in the conventional optical cell 27, various types of seal material made of synthetic resins, silver brazing, gold brazing, and the like are used.
Furthermore, in order to perform stable gas concentration measurement continuously, the transparency of the light transmission window material forming the optical cell 27 needs to be maintained stable for a long period of time, and if the transparency changes over time, stable gas concentration measurement becomes difficult.
However, in a conventional gas concentration meter, as mentioned above, in fastening and retaining various types of structures forming the optical cell 27, seal materials made of various types of synthetic resins and silver brazing, gold brazing and other measures are used to ensure air tightness, and thus there is a risk that the seal materials made of synthetic resins, silver brazing, gold brazing and other measures become the source of gases and particles released into organic feedstock material gases. In fact, there is the problem that the purities of the gases are lowered by the discharge of particles. Thus, it is desirable to avoid using silver brazing or gold brazing in the gas supply system for semiconductor manufacturing.
Moreover, since quartz glass is often used as a material of a light transmission window in a conventional gas concentration meter, there is still a problem that, in measuring the concentration of an organic feedstock gas with high corrosiveness or high deposition property, the transparency of the light transmission window is lowered at an early stage due to the corrosion of the window and the deposition of the feedstock, and consequently stable measurement of the concentration of the feedstock gas cannot be performed.
Meanwhile, in place of using the seal materials and the like, the ideas of mechanically fastening various types of structures onto necessary portions directly by nipping have been conceived. However, it is difficult to ensure air tightness by fastening directly or by nipping, and in the case where the member to be fastened is a panel material made of brittle-fracturable material such as quartz glass or sapphire, fastening by mechanical nipping without using any seal material cannot easily provide high sealing property.
As mentioned above, a conventional concentration meter of the photometric analysis system has many problems left to be solved, for example, reducing the size and costs of the facility, ensuring the stability in the accuracy of concentration measurement, maintaining high purity of gas and retaining the air tightness of gas. Therefore, measures for ensuring the sealing property between the light transmission window material and the structure, preventing lowered purity of gas caused by the use of the seal material and preventing lowered transparency of the light transmission window material caused by the corrosiveness of an organic feedstock gas have been urgently sought.
Among them, in particular, providing measures which allow firmly fastening and retaining the light transmission window material forming the major portions of the sensor portion without using any seal material or the like with high air-tightness has been urgently demanded.